well, because mods are busy and haven`t take a look already to the report. The "unhandled" number will decrease as soon as they take some action.
That's exactly what I'm highlighting. If refferel link involved in a report, mods are not looking at those reports and save it for another time. But other low value/spam posts like "Good project", "great project" are marked good within few minutes. What I'm thinking is those two scenarios to be considered as similer situations since both violate the forum rules. We can say it by just looking at ref link only. No rocket science for further study.
Sometimes those unhadled can be marked as bad as well. I have experience, that one of my report has been marked as bad.(actually it isn't bad)
I have had some similar experiences, but you know, mods are humans too. I suspect mostly the deleted posts you are talking about come from the patrol page, and they are erased/trashed or banned fast.
As I told you once, do not take it too personally, continue reporting and do not care too much for your accuracy, if you think a post should be reported, then report it, but do not get obsessed with the result.